1. Field of the Invention
The present invention relates to a capacitive occupant sensor.
2. Description of Related Art
JP-A-2008-38077, JP-A-2008-506962, JP-A-2007-101489, JP-A-2000-65658 or US 2008/0277910 A1 discloses a device to detect an occupant seated on a vehicle seat.
JP-A-2008-38077 discloses antenna electrodes arranged on a base fabric as an antenna to detect an occupant. The antenna electrode has a loop shape, and a center part of the antenna electrode has an opening open in a vehicle, left-and-right direction.
JP-A-2008-506962 discloses an electrode of an occupant detecting device. The device has a linear-shaped conductive passage extending in a vehicle front-and-rear direction. The conductive passage has T-shaped projections extending to both sides of the electrode.
JP-A-2007-101489 discloses a seat of an occupant detecting device. The seat is divided into two sections in a seat width direction, and is further divided into two sections in a seat front-and-rear direction. Thus, the seat is divided into the four sections. The sections located adjacent to each other in the seat front-and-rear direction are connected with each other through a first elastic portion having a bent shape. The sections located adjacent to each other in the seat width direction are connected with each other through a second elastic portion.
JP-A-2000-65658 discloses a seating sensor made of a film. The seating sensor has a left section and a right section. A clearance is defined between the left section and the right section in a vehicle left-and-right direction, when no occupant is seated on a vehicle seat. The left section and the right section are to be connected with each other, if an occupant is seated on the vehicle seat.
US 2008/0277910 A1 discloses U-shaped film sensors arranged in series. Thus, a vehicle seat is deformable in both of a front-and-rear direction and a left-and-right direction.
Because the opening of the antenna electrode of JP-A-2000-38077 opens in the vehicle left-and-right direction, a vehicle seat can be deformed in a vehicle front-and-rear direction, but the vehicle seat cannot be deformed in the vehicle left-and-right direction.
Because the linear-shaped conductive passage of JP-A-2008-506962 is located to extend in the vehicle front-and-rear direction, a vehicle seat cannot be deformed in the vehicle front-and-rear direction.
In JP-A-2000-38077 or JP-A-2008-506962, the vehicle seat is deformable in a first direction, but is not deformable in a second direction perpendicular to the first direction, because a linear member located in the vehicle seat extends in the second direction. Therefore, it is difficult to raise a comfortableness of the vehicle seat.
Because the vehicle seat of JP-A-2007-101489 is divided into the four sections, the vehicle seat is deformable in the seat width direction and the seat front-and-rear direction. However, because each section does not have an opening, each section is difficult to have a deformation.
Similarly, because each section of JP-A-2000-65658 does not have an opening, each section is difficult to have a deformation.
In JP-A-2007-101489 or JP-A-2000-65658, the vehicle seat has a deformable part, but each section of the vehicle seat is not deformable. Each section has a linear member, and the linear member cannot have a bending in an extending direction of the linear member. Therefore, it is difficult to raise a comfortableness of the vehicle seat.
The vehicle seat of US 2008/0277910 A1 is deformable in both of the front-and-rear direction and the left-and-right direction, due to the U-shaped film sensors arranged in series. However, an electrode arranged in the vehicle seat cannot have a necessary capacitance, because an area of the electrode cannot be made large.